Arthur d



UNITED STATES PATENT OFFICE.

ARTHUR D. LITTLE, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO THE AMERICANVISCOSE COMPANY, OF SAME PLACE.

CARBON FILAMENT AND METHOD OF MANUFACTURING SAME.

SPECIFICATION forming part of Letters Patent No. 532,468, dated January15, 1895. I Application filed June l8, 1 894. Serial No. 514,956. (Nospecimens.)

To all whom it may concern.-

Be it known that I, ARTHUR D. LITTLE, of Boston, in the county ofSuffolk and State of Massachusetts, have invented an Improvement inCarbon Filaments and Methods of Manufacturing the Same, of which thefollowing description is a specification.

My invention relates to the composition and manufacture of filaments forincandescent lamps, whereby the percentage of carbon contained in thefilaments is increased, and consists in the employment of a compound ofcellulose and an organic acid, as for instance, acetic acid or itsanhydride, the re sulting product being subsequently formed into stripssuitable for filaments, and then carbonized.

Carbon filaments have heretofore been prepared from various fibrousmaterials, as bamboo, card board, cotton and linen thread, and fromcellulose more or less nearly approaching a condition known as amorphouscellulose, by ignition of the material out of contact with the air, andsubsequent exposure of the heated filaments to the vapor of hydrocarbonsafter the usual manner which is well known.

It is difficult to prepare from cellulose, in its fibrous form,filaments which are entirely homogeneous in structure, and in which thecarbon is distributed with precise uniformity throughout their lengths,and such inequalities of structure, and unequal distribution of thecarbon cause the resistance of the filaments to vary at differentpoints.

In accordance with this invention the cellulose is treated with anorganic acid or its anhydride, such for instance, as acetic anhydride,and the reagent thus employed, itself being composed largely of carbon,does not introduce any objectionable material which must thereafter beremoved.

In carrying out my invention I prefer to take a quantity of cellulose,with six to eight times its weight of acetic anhydride, and heat thesame in a sealed tube, to say 180 centigrade, producing a solution ofcellulose acetate, and then form the filament by forcing the solutionthus obtained through a small aperture into water in which the celluloseacetate is insoluble, or by forming i into sheets of suitable thicknesswhich may be done by pouring the solution upon glass, allowing it todry, then dipping it into Water, and stripping off the sheet, andfinally drying and cuttin git into strips. The strips obtained by eithermethod are then carbonized and flashed as usual.

The cellulose acetate thus produced contains a large percentage ofcarbon, and the structure of the filament formed is thereforehomogeneous, and no inequality appears in its resistance.

I claim 1. The material for carbon filaments for incandescent lampsherein described consisting of a compound of cellulose and an organicacid.

2. The material for carbon filaments for incandescent lamps hereindescribed composed essentially of cellulose acetate, produced. bytreating cellulose with acetic anhydride.

3. The method herein described of making filaments .for incandescentlamps which consists in heating cellulose with an organic acid to a hightemperature, forming filaments of the product thus obtained, andsubsequently carbonizing them.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing Witnesses.

ARTHUR D. LITTLE.

Witnesses:

B. J. NoYEs, FLORENCE H. DAVIS.

